Abstract
Internal circulation cabinets, equipped with adsorbents for emitted volatile organic compounds (VOCs), are extensively used to store organic solvents in Taiwanese university and hospital laboratories. This work evaluates how ketone and isopropanol (IPA) respectively influence the methyl ethyl ketone (MEK) adsorption capacity of a hydrophobic molecular sieve (MS) with a high Si/Al ratio of 1000, HiSiv 1000, manufactured by UOP LLC Corporation, USA. Experimental results for MEK at concentrations from 113 to 2815 ppm reveal that the MEK adsorption capacity is linearly expressed as the natural logarithm of adsorption time (ln (t)) at the constant temperature 27 o C and relative humidity 72 ± 3%. The variations in the simulated MEK equilibrium adsorption capacity (Qe, g MEK/g MS) and concentration (C, ppm) are closely fitted using a Langmuir isotherm. Lower VOC concentration ratios less than 0.17 for mixing acetone and IPA respectively with MEK rarely affect the MEK adsorption by HiSiv 1000. However, the effect of competitive adsorption, which evidently reduces the adsorption capacity of MEK, is related to the higher mixture concentration ratio (> 0.80) of IPA to MEK. The experimental results show that the hydrophobicity characteristics of MEK, acetone and IPA were responsible for variation in adsorption capacity of hydrophobic molecular sieve. Working parameters of adsorbent materials in the internal circulation cabinet have been also provided for preventing breakthrough of VOC adsorption by the molecular sieve.
Highlights
Many organic solvents have been used in laboratories of Taiwanese universities and hospitals
Variations of adsorption capacity with volatile organic compounds (VOCs) concentrations methyl ethyl ketone (MEK) adsorption tests were performed using the molecular sieve at an inlet concentration ranging from 113 to 4564 ppm, over periods of 60–600 min at 27oC
Working parameters for the internal circulation cabinet To prevent the over-adsorption of VOC by HiSiv 1000, the operation parameters are recommended as follows
Summary
Many organic solvents have been used in laboratories of Taiwanese universities and hospitals. These volatile organics with low boiling points are typically stored in sealed storage cabinets to prevent the unhealthy effects of gaseous volatile organic compounds (VOCs) on workers. Mobile cabinets with internal circulating adsorption system (Fig. 1) are widely employed to store solvents in indoor area. The adsorbent, currently molecular sieves (MS) in Taiwan, must be periodically renewed to prevent the over-adsorption of VOCs by the adsorbent under breakthrough. The detailed adsorption characteristics of molecular sieves, used by local manufacturers of storage cabinets, have not been thoroughly examined, nor has the adsorption performance been well evaluated.
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